I absolutely love the way you break this down . Thank you for being such a great help because the majority of instructors forget about the end questions involving largest motor increase , and never teach the wire and ground size here in Washington
Thank you Raymond! I've seen the motor increase at the end mess up more students than just about anything else on these types of calculations. Wire and ground size are definitely important to know, although table 310.12 in the 2020 NEC has made that a bit easier. Thanks again!
Thanks for these videos! I am a first year in Oregon and this is helping me polish off my knowledge for rezi. This channel is helping me advance my knowledge well beyond my year in school! This channel is a great asset to me! Thank you!
Thank you for this info. Had to get my whole box replaced about 7 years ago and wish I had upgraded to 150 or 200 service at that time. I'm thinking of updating some of my gas utilities to electric and going by your example alone it looks like I won't be able to without something in that range, no to mention probably adding EV charging at some point.
Hey coach question, so since we used Heat omitted the A/C Because its a non coincident load, wouldn't our biggest motor would be the disposal use the 25% ? I saw this question in the comments but im still confused coach
After Reviewing the 2020 NEC, I actually realized that there was a revision that requires if the A.C. motor was omitted in 220.60 but was the largest motor, you are still required to make the adjustments for your largest motor based on it. So if your state is still on the 2017 or older, you will still omit it from your calculations; however if your state has adopted the 2020 or 2023, you will need to include it even if it was omitted assuming it was your largest motor in the calculation!
I thought that when you chose the heat and omitted the ac from the larger of the two loads. That you could no longer count the ac as the largest motor factor. Would you have to chose the next largest motor and not the ac even though it’s the largest, because it was omitted in a previous step due to the heater being larger in VA than the Ac?
Prior to the 2020 NEC you would be correct, but in the 2020 and 2023 there was an update that now requires the A.C. to be used even if it was originally omitted from the calculation. If you are in a jurisdiction that uses the 2017 NEC or older, than you are correct; you would use the next largest motor if the A.C. was the largest.
I wanted to ask whether it is correct to use the 25 of A/C even though it wasn't used for heat in part 4. I have been explained that if AC is ur biggest motor load but you have higher load for heating and used that for part 4, you shall use the next biggest motor load as the higher heating value makes up for 25 of AC motor and when heat is used ac isn't being used.
shouldnt the main service breaker be sized based off the load calculations amperage being no more than 80% of the main service breaker size? with a total load calculation of 156A using 175A main panel, the load is 89% of the main breaker size. according to the conductor sizing table a 175a service would use a minimum size #1/0 awg conductor wich is rated 150A at 75° column. 150A wire supplying a 156A load doesnt seem very wise to me. am i missing something here?
Wish you would’ve expanded on main breaker sizes and water ground sizing. I’ve never seen a 175 amp main before. All I’ve seen is 125, 150 and 200 amp main breakers in residential.
I'm having a difficult time understanding when to take into consideration continuous and non continuous loads when sizing the service/feeders. Examples in the back of the code book show this being added to the calcs, but in your example and in Mike Holts study guide it's not used. I get that the 125% is already included in the 3va/ft Gen Lighting, but what about other loads?
Hi Brady, the answer to that question is pretty simple, but it's simply that the code does not require any adjustments for continuous loads unless they are specifically called out in the calculation. An example of this would be that in step 7, we add an additional 25% for the largest motor load. For appliances and other similar loads, since we are using nameplate ratings for the loads, those adjustments would already be included from the manufacturer. Hope that helps!
Thanks for this easy to follow example. We just upgraded our service from 100A to 200A, in anticipation of gas appliances being phased out, and electric cars being in the future. We do have rooftop solar to offset our hot tub.
That is done in order to meet 220.14(J), which requires that for dwelling units we include a load of not less than 3 VA per square foot. Hope that helps!
Why dividing by 240 at the end if some equipment have the KW demand @ 120? I think we should calculate the amps for the 240V demand and for the 120V demand separately, then add the amps .
What I don't understand is that I am using Tom Henry's material and when dealing with Step 8. In his example he has a 5hp single-phase 240v A/C Motor and a 1/2 hp compactor. However, instead of selecting the AC unit for Step 8 he selects the 1/2 hp compactor. He does this in several examples and it doesn't seem correct. Because in the 5hp motor it's 6720VA but in the 1/2hp compactor it's only 1176 VA. Any thoughts as to why Tom Henry is calculating Residential Services differently than how you do it?
Yes Tom Henry is correct. Since the A/C load is ommited you are not supposed to use that for your largest motor. He should have used the Disposal in this example
@@jamesaglasscock What do you mean the A/C load is omitted? Does that mean that because we selected the Heat 9600VA in Step 4 that you now basically forget about the AC for any other calculations?
@@PPyle Yes. If you use the heating load instead of the a/c load in your calculation you no longer use the a/c motor for your largest motor in your calculation. You find the next largest which usually ends up being the disposal. This is how I was taught and I believe to be the correct method .
@@PPyle HI there, James g is absolutely correct; since the AC load was not used in the earlier steps, we do not count it as the largest motor load when trying to do step 8.
It’s because you only have (1) 15kw range so if you look at “1” in the number of appliances column then go all the way over to column C the maximum demand would be 8kw but you have to also apply note 1. I like to just multiply by 115% instead of doing what he did in this case but either way works.
Can/should a microwave be calculated together with the fixed appliances (step 5)? or is it under the cooking equipment (step 6)? I have a split wall oven and cooktop set-up that will be connected to the same 240v circuit and I am using the table under NEC 220.55 to do the calculation. I am not sure whether I need to include the microwave in the calculation. Table 220.55 says it is for household cooking appliances over 1-3/4 kw. The microwave specs says that the "AC Power Required 1500W / 13.5 A" which is below the threshold for table 220.55 by itself but not when combined with the wall oven and cooktop. Thanks for the video - it has been very helpful.
I can see that 220.53 says the Microwave cannot be included in the fixed appliances either because the demand factor does not apply to "(1) Household electric cooking equipment that is fastened in place.", so is it just included by itself in the calculations as a line after cooking appliances, AC etc. at the nameplate rating?
what if there were 2 ac.? would i consider the addition of both for largest motor calculations? how about heat against ac? same applies or add both then compare to heat?
Prior to the 2023 NEC, this most likely would have been considered a fixed in place appliance. In the 2023 NEC, however, 220.57 requires including either 7200 watts or the nameplate rating (whichever is larger) for each charger installed.
Regarding the 5hp AC unit @ 240....does this account only for the inside unit with the fan? What about the outside unit with the compressor?....Also when in heat mode do you add the 5hp motor VA to the kw of the heating element? And final question.....what if the HVAC unit is a heat pump, naturally the heating element only operates when the difference in the temp requires?....if someone can supply reference page in the book
Hello and good! Very nice video. Just confused with regards to additional 25% of the largest motor. Yes, the acu has the largest FULL LOAD CURRENT among all the given motors, however, ACU was omitted in the calculation because its VA is less than the electric space heat. Can you please give a clarification on this. Thanks much for your response.
Hello, thank you for your time. I have a question. Is this method calculation based on NEC2020? I can't find a code reference for Step 1 in the NEC2020 220.12 (J) if it is. I will assume that is a typo since I found that info in 220.14(J) Dwelling Units.
to me, the horsepower table in the NEC doesn't make sense. if one(1) horsepower equals 746 watts. five(5) horsepower is 3730w ÷ 240v does not equal 28 amps.
Hello, one horsepower being equal to 746 watts applies to the output of the motor, not the input. Meaning since a 5 horsepower motor outputs the equivalent to 3,730 watts, in order for the input needed to be 3,730 watts as well, that motor would have to have an efficiency rating of 100% which we know is impossible. The tables given in the NEC are based on a very low efficiency factor so that wide variety of motors may be used. If the circuit were sized based on a motor with a 95% efficiency, factor, that would mean you would never be able to replace that motor with a lower efficiency one since the input circuit would be undersized. Hope that helps!
310.12 states Single one-family dwellings and individual delling units of two family and multifamily dwellings, service and feeder conductors supplied by a single-phase, 120/240 volt system shall be permitted to be sized in accordance with 310.12(A) which state: "Serivce rated 100 amps through 400 amps supplying entire load associated iwht a one-family dwelling, or the service conductors sup;lying the entire load associated with an individual dwelling unit in a two family or multifamily dwelling, shall be permitted to have an ampacity of not less than 83 percent of the service rating. Does this mean we can size the conductors at 83 percent of the 155.9 amps we calculated?
You are close to correct; once you have calculated the load of the building (in this case 155.9 amps), you then have to pick out a service size based on table 240.6(A). In this case, that would mean going up to a 175 amps service. The code section you reference then allows us to size the conductors for the service at 83% of the 175 amp service we selected, which would be either a 1/0 copper or 3/0 aluminum conductor. Table 310.12 does this math for you. Hope that helps!
@@electrical1019 ah ok so that 83% is already included in 310.12 table. Thank u sir! U should do a video on how to calculate branch circuit breaker and wire size
Per 220.60, we are able to include the heat or AC unit and not the other since they are a noncoincident load. Since we included the larger of the two (the heat) there is not reason to include the A.C. We do, however, have to account for part of it in step 8 if the A.C. was our largest motor!
We only multiple by 25% since 100% of the load as already been accounted for in step #4. So in essence, in step number for we are only adding the additional amount needed to reach 125%, which would be 25%. Hope that helps!
Thanks for the video, but I have a question to the step 8 “largest motor is to be increased 25%”. I thought it has to be 6720*1.25, or I misunderstood this step
Hi Peter, for both an EV charger as well as a pool heater/pool pump, I would consider those to be fixed in place appliances. As such, they would be included in step 5.
Do you have to use the figures in the book for hp conversion? The conversion is not exact, and I'm wondering if that would mess up your answer during the exam
We already included 100% of the load in previous steps (either step 4 for A.C. equipment or step 5 for appliance loads) so in step 8 we only need to include an additional 25% to reach a total of 125% for the entire calculation. Hope that helps!
I'm sorry, but wouldn't a 150 Amp Service, be sufficient, since 2014, where the code states your service only needs to support 83% of the load? Your stated load of 156 Amps @ 83% = 129 Amps. Correct?
HI Joey, the rule you are referring to is in regard to the conductor size, not the actual load size. Meaning when you are sizing conductors for a service they only need to be 83% of the ampacity of the service. That is why we can use 4/0 AL wires on a 200A service even though 4/0 AL is not rated for 200 amps. Hope that helps!
Thanks for the video! In reguards to the A/C how do you know to use the alternating current single phase table? as every 240V Air conditioner in the field uses direct current (nuetral is never used, just the two powers.) How do we know to choose alternating current table over the direct current table?
The 2 lines is not direct current. U grossly misunderstand what dc is. DC stands for direct current which comes from a source like a battery and solar. 120 volts is simply half of 240. Neutral is part of the same system of the 240 but is tapped in the center of the secondary transformer of your power. Neutral simply carries the imbalance in your house. 240 is already a balanced system but it is still very much so AC in a single phase system.
Yes, table 310.12 was added in 2020. To find the conductor size needed using a 2014 code, you can simply multiply your service size by 83% and then use the resulting ampacity to select a conductor from table 310.16.
On our video "Graphics for the national electrical code" we provide a link to download them as well as provided step by step instruction on putting them in your code book!
Thank you for your videos they help tremendously. I have a question. When calculating the amps from horsepower the formula is : (Hp x 746)/(volts x phase x eff x pf) Why not use that formula if the info is given? Thx and God bless
VA is not "Volts times Amps" that's Watts. It is Volt-Amperes in the same sense that Foot-Pounds are not simply feet times pounds but a "moment arm" of so many pounds across at the end of a foot long lever.
You are absolutely correct; however, in terms of practical application when doing a load calculation and when sizing branch/feeder circuits in the field, they are treated the same. Since this material is also intended to be a theory or electrical terminology instructional video, we don't try to explain this during the lesson. We do hope to be able to upload some material on theory including the difference between real power and apparent power, etc. in the future though!
From where the table 430.248 get the values? Is not 1hp=746watts? Why if using the table, multiply 28*240 instead of 28*230 to get the power of 5hp? It looks like that motor is 55.5% efficient, so 44.5% of the power input is lost. Seems like the worst situation is used for calculating the loads.
Saludos, Los vatios son iguales a los VA, solo cuando las cargas son resistivas. O sea Factor de potencia = zero. Cuando hay hay cargas inductivas y/o capacitivas, el angulo entre la coriente y el voltaje no es zero(0). Watts= VA COS zeta Zeta es el angulo entre la Watts y VA.
My question pertains to selection of conductors. I selected my conductors from Table 310.16 under the 75 degree column, since it wasn't specified what the terminal ratings were. I selected 2/0 copper rated at 175 amps rather than 1/0 rated at 150 amps. When should you use Table 310.16 over Table 310.12? Thank you for this video btw. You helped clear up a couple of my other questions. It's tough to not be confused with General/Optional Methods involving single and multi-family dwellings.
Hi Mac, Table 310.12 can only be used according to the requirements of 310.12(A) through (D), which basically say for any dwelling using a single phase service you are allowed to use table 310.12 to size your conductors based on the service size. The only point of table 310.12 is that is already does the math of 310.12(A), which states you can size your conductors based on 83% of the service size. In other words, if we were sizing conductors for a 200A service, we would only need conductors rated at 83% of 200A, which would be 166A. As we can see in table 310.12, for a 200A service a #2/0 copper wire is called out, which is rated at 175A using the 75 degrees column. Hope that helps!
In step #8 you didn't increase the motor by 25% according to the instructions, you just took 25% of the motor. In other words, instead of using 125% of the AC motor, you only used 25%. Why?
He added that to the total. So it actually is an increase. I thought the same thing at the time but then I saw what he did with it and it still works. The whole point is to get the total watts to find the minimum amp needed. As long as those watts are all added to the total then it works.
I'm still confused.. if we removed the motor because of step 4 heating and ac.. why are we using the motor.. also where did 25% in lue of 125% come from? Thanks
I was taught that if you omit the AC motor you don’t use that for 125% of your largest motor. So the way I was taught was I would use 125% of the largest motor I used in my calculations which would be the garbage disposal.
Quote from @electrical1019: Prior to the 2020 NEC you would be correct, but in the 2020 and 2023 there was an update that now requires the A.C. to be used even if it was originally omitted from the calculation. If you are in a jurisdiction that uses the 2017 NEC or older, than you are correct; you would use the next largest motor if the A.C. was the largest.
Holy shit! As someone who went to college for electrical engineering, this is the most convoluted shit I have ever seen. Great way to make simple math seem complicated. WOW! I TRULY AM AT A LOSS. 😅
Hi there, the NEC doesn't really have a stance on what load has to be considered for a sub panel, other than if continuous loads, motor loads, etc. will be fed from the panel in which case the 125% rule would apply to the breaker supplying the panel. I recommend sizing sub panels based on the actual load needing to be served (i.e., if you are feeding a combined total of 20,000 watts on a sub panel then I would size that to breaker able to carry that much load). Hope that helps!
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This was probably the best explanation I’ve heard yet. Simple and understandable breakdown of the steps.
Best explanation yet of service load calculation. Wish my instructors taught this way. Thanks
I absolutely love the way you break this down . Thank you for being such a great help because the majority of instructors forget about the end questions involving largest motor increase , and never teach the wire and ground size here in Washington
Thank you Raymond! I've seen the motor increase at the end mess up more students than just about anything else on these types of calculations. Wire and ground size are definitely important to know, although table 310.12 in the 2020 NEC has made that a bit easier. Thanks again!
Thanks for these videos! I am a first year in Oregon and this is helping me polish off my knowledge for rezi. This channel is helping me advance my knowledge well beyond my year in school! This channel is a great asset to me! Thank you!
very good. you simplified everything and went at a pace that everyone could follow.
great explanation! I also agree, i wish all instructors, trainers, teachers and professors would teach this effectively
Much appreciated, this question burned me on my master's, retaking it next week!
This was a very helpful refresher before going to take my Journeyman Exam, thank you kindly!!
Explained it better than my school. Thank you.
What a great, simple breakdown! ⚡
Thank you for this info. Had to get my whole box replaced about 7 years ago and wish I had upgraded to 150 or 200 service at that time. I'm thinking of updating some of my gas utilities to electric and going by your example alone it looks like I won't be able to without something in that range, no to mention probably adding EV charging at some point.
This has always been my struggle when testing. I now will understand it better for testing purposes.
Glad we were able to help!
Hey coach question, so since we used Heat omitted the A/C Because its a non coincident load, wouldn't our biggest motor would be the disposal use the 25% ? I saw this question in the comments but im still confused coach
After Reviewing the 2020 NEC, I actually realized that there was a revision that requires if the A.C. motor was omitted in 220.60 but was the largest motor, you are still required to make the adjustments for your largest motor based on it. So if your state is still on the 2017 or older, you will still omit it from your calculations; however if your state has adopted the 2020 or 2023, you will need to include it even if it was omitted assuming it was your largest motor in the calculation!
I thought that when you chose the heat and omitted the ac from the larger of the two loads. That you could no longer count the ac as the largest motor factor.
Would you have to chose the next largest motor and not the ac even though it’s the largest, because it was omitted in a previous step due to the heater being larger in VA than the Ac?
Prior to the 2020 NEC you would be correct, but in the 2020 and 2023 there was an update that now requires the A.C. to be used even if it was originally omitted from the calculation. If you are in a jurisdiction that uses the 2017 NEC or older, than you are correct; you would use the next largest motor if the A.C. was the largest.
Does the 80% percent rule not apply to the final calculation for determining what size service you need?
same thing I was thinking
the NEC 2017 doesn’t have table 310.12. how can i find the size of the wire without table 310.12
this was amazing. thank you so much for sharing your knowledge with the rest of us.
Thank you so much!
I wanted to ask whether it is correct to use the 25 of A/C even though it wasn't used for heat in part 4. I have been explained that if AC is ur biggest motor load but you have higher load for heating and used that for part 4, you shall use the next biggest motor load as the higher heating value makes up for 25 of AC motor and when heat is used ac isn't being used.
I have the same question
shouldnt the main service breaker be sized based off the load calculations amperage being no more than 80% of the main service breaker size? with a total load calculation of 156A using 175A main panel, the load is 89% of the main breaker size. according to the conductor sizing table a 175a service would use a minimum size #1/0 awg conductor wich is rated 150A at 75° column. 150A wire supplying a 156A load doesnt seem very wise to me. am i missing something here?
My garbage disposal says 6.3a 120v and 1/2 hp. Do I use the amps given on the garbage disposal, or do I use the amps given in the code book?
For the sake of this calculation, you would use the NEC stated ampacity.
I love the way you explain things!
Thank you!
Wish you would’ve expanded on main breaker sizes and water ground sizing. I’ve never seen a 175 amp main before. All I’ve seen is 125, 150 and 200 amp main breakers in residential.
@@kennyphelps9237you are correct, so you would put a 200 amp panel in the house
Hey do you have a video example of calculation of demand from multiple 120/240 ranges?
I'm having a difficult time understanding when to take into consideration continuous and non continuous loads when sizing the service/feeders. Examples in the back of the code book show this being added to the calcs, but in your example and in Mike Holts study guide it's not used. I get that the 125% is already included in the 3va/ft Gen Lighting, but what about other loads?
Hi Brady, the answer to that question is pretty simple, but it's simply that the code does not require any adjustments for continuous loads unless they are specifically called out in the calculation. An example of this would be that in step 7, we add an additional 25% for the largest motor load. For appliances and other similar loads, since we are using nameplate ratings for the loads, those adjustments would already be included from the manufacturer. Hope that helps!
Thanks for this easy to follow example. We just upgraded our service from 100A to 200A, in anticipation of gas appliances being phased out, and electric cars being in the future. We do have rooftop solar to offset our hot tub.
310.12 (a) and (b) say you can apply 83% demand factor to your Service and Feeders. (100A-400A)
You're absolutely correct! Table 310.12 has the 83% figured into the sizes provided already.
Thank you so much for your great explanation.
We’re did the 25% from step 8 come from I check 220.50 just directs you to motor and there nothing in those sections about 25%?
Step 8 comes from 430.22 and/or 430.24!
Did he do that part wrong?
I think he reduced by 75% not increased by 25%.
Or multiplied by 125% as in the 430.22 part.
Can anyone explain why he's multiplying the square footage by 3va in the begining??
That is done in order to meet 220.14(J), which requires that for dwelling units we include a load of not less than 3 VA per square foot. Hope that helps!
Why dividing by 240 at the end if some equipment have the KW demand @ 120? I think we should calculate the amps for the 240V demand and for the 120V demand separately, then add the amps .
What I don't understand is that I am using Tom Henry's material and when dealing with Step 8. In his example he has a 5hp single-phase 240v A/C Motor and a 1/2 hp compactor. However, instead of selecting the AC unit for Step 8 he selects the 1/2 hp compactor. He does this in several examples and it doesn't seem correct. Because in the 5hp motor it's 6720VA but in the 1/2hp compactor it's only 1176 VA. Any thoughts as to why Tom Henry is calculating Residential Services differently than how you do it?
Yes Tom Henry is correct. Since the A/C load is ommited you are not supposed to use that for your largest motor. He should have used the Disposal in this example
@@jamesaglasscock What do you mean the A/C load is omitted? Does that mean that because we selected the Heat 9600VA in Step 4 that you now basically forget about the AC for any other calculations?
@@PPyle Yes. If you use the heating load instead of the a/c load in your calculation you no longer use the a/c motor for your largest motor in your calculation. You find the next largest which usually ends up being the disposal. This is how I was taught and I believe to be the correct method .
@@jamesaglasscock That makes sense, thank you so much for the help.
@@PPyle HI there, James g is absolutely correct; since the AC load was not used in the earlier steps, we do not count it as the largest motor load when trying to do step 8.
Why is the EVSE load (7200 Watts or nameplate) not factored in to this calculation?
Great Video. But could some onme help me out? 13:06 Where in column C does it say to round it to 8 kw?
It’s because you only have (1) 15kw range so if you look at “1” in the number of appliances column then go all the way over to column C the maximum demand would be 8kw but you have to also apply note 1. I like to just multiply by 115% instead of doing what he did in this case but either way works.
Can/should a microwave be calculated together with the fixed appliances (step 5)? or is it under the cooking equipment (step 6)?
I have a split wall oven and cooktop set-up that will be connected to the same 240v circuit and I am using the table under NEC 220.55 to do the calculation.
I am not sure whether I need to include the microwave in the calculation.
Table 220.55 says it is for household cooking appliances over 1-3/4 kw.
The microwave specs says that the "AC Power Required 1500W / 13.5 A" which is below the threshold for table 220.55 by itself but not when combined with the wall oven and cooktop.
Thanks for the video - it has been very helpful.
I can see that 220.53 says the Microwave cannot be included in the fixed appliances either because the demand factor does not apply to "(1) Household electric cooking equipment that is fastened in place.", so is it just included by itself in the calculations as a line after cooking appliances, AC etc. at the nameplate rating?
what if there were 2 ac.? would i consider the addition of both for largest motor calculations? how about heat against ac? same applies or add both then compare to heat?
Also, where do you place a Electric Vehicle Charger, 240V, 50A, 12kW? (I guess this is also a continues load)
Prior to the 2023 NEC, this most likely would have been considered a fixed in place appliance. In the 2023 NEC, however, 220.57 requires including either 7200 watts or the nameplate rating (whichever is larger) for each charger installed.
Regarding the 5hp AC unit @ 240....does this account only for the inside unit with the fan? What about the outside unit with the compressor?....Also when in heat mode do you add the 5hp motor VA to the kw of the heating element? And final question.....what if the HVAC unit is a heat pump, naturally the heating element only operates when the difference in the temp requires?....if someone can supply reference page in the book
Please do and optional method calculation! Your videos are exceptional! This is exactly how I learn.
Hi Matthew, we will be making a series of new videos over the summer and will make sure to include one for the optional method!
Hello and good! Very nice video. Just confused with regards to additional 25% of the largest motor. Yes, the acu has the largest FULL LOAD CURRENT among all the given motors, however, ACU was omitted in the calculation because its VA is less than the electric space heat. Can you please give a clarification on this. Thanks much for your response.
Question: wouldn’t the largest motor for step 8 be 9.6kw to be increased by 25% not 6,720va because of no coincidence load. Am I wrong?
Great explanation!! But shouldn’t the general lighting be included in this case?
Hello, thank you for your time. I have a question. Is this method calculation based on NEC2020? I can't find a code reference for Step 1 in the NEC2020 220.12 (J) if it is. I will assume that is a typo since I found that info in 220.14(J) Dwelling Units.
to me, the horsepower table in the NEC doesn't make sense. if one(1) horsepower equals 746 watts. five(5) horsepower is 3730w ÷ 240v does not equal 28 amps.
Hello, one horsepower being equal to 746 watts applies to the output of the motor, not the input. Meaning since a 5 horsepower motor outputs the equivalent to 3,730 watts, in order for the input needed to be 3,730 watts as well, that motor would have to have an efficiency rating of 100% which we know is impossible. The tables given in the NEC are based on a very low efficiency factor so that wide variety of motors may be used. If the circuit were sized based on a motor with a 95% efficiency, factor, that would mean you would never be able to replace that motor with a lower efficiency one since the input circuit would be undersized. Hope that helps!
@@electrical1019 that does help. thanks for explaining it to me.👍
@@electrical1019 I needed that explanation thank you.
This guy is out here doing gods work, thank you sir!
310.12 states Single one-family dwellings and individual delling units of two family and multifamily dwellings, service and feeder conductors supplied by a single-phase, 120/240 volt system shall be permitted to be sized in accordance with 310.12(A) which state: "Serivce rated 100 amps through 400 amps supplying entire load associated iwht a one-family dwelling, or the service conductors sup;lying the entire load associated with an individual dwelling unit in a two family or multifamily dwelling, shall be permitted to have an ampacity of not less than 83 percent of the service rating.
Does this mean we can size the conductors at 83 percent of the 155.9 amps we calculated?
You are close to correct; once you have calculated the load of the building (in this case 155.9 amps), you then have to pick out a service size based on table 240.6(A). In this case, that would mean going up to a 175 amps service. The code section you reference then allows us to size the conductors for the service at 83% of the 175 amp service we selected, which would be either a 1/0 copper or 3/0 aluminum conductor. Table 310.12 does this math for you. Hope that helps!
@@electrical1019 ah ok so that 83% is already included in 310.12 table. Thank u sir! U should do a video on how to calculate branch circuit breaker and wire size
@@dougfoster445 We have some videos on that topic up currently!
@@electrical1019 thanks man! Looking into it now!
So are we not including the AC unit watt calculation?
Per 220.60, we are able to include the heat or AC unit and not the other since they are a noncoincident load. Since we included the larger of the two (the heat) there is not reason to include the A.C. We do, however, have to account for part of it in step 8 if the A.C. was our largest motor!
Why did you not multiply AC at 125% for continuous duty? Couldn't that possibly make it a greater load?
We only multiple by 25% since 100% of the load as already been accounted for in step #4. So in essence, in step number for we are only adding the additional amount needed to reach 125%, which would be 25%. Hope that helps!
hi!; great video. question, where do you place a gas dryer, 120V, 6A, 720W?
The NEC does not place any requirements on load calculations for gas appliances, including dryers.
What happened if the test says you have two small appliances and one laundry ?
Per 220.52(A) and (B) you would need to include 1500 volt-amps per circuit.
Thanks for the video, but I have a question to the step 8 “largest motor is to be increased 25%”. I thought it has to be 6720*1.25, or I misunderstood this step
1.25 would be 125%
Question; how about when its multifamily dwelling? What formula or steps do I use?
For multifamily dwelling you would reference the steps outline in 220.84. Hope that helps!
since we omitted the AC doesn't the motor go with it?
Thats how its done according to the Tom Henrys load calculations book. This caught me by surprise too.
Where do we add EV car charges in this? What if they have more than one EV car chargers? Is a pool heater and pool pump considered as an appliance?
Hi Peter, for both an EV charger as well as a pool heater/pool pump, I would consider those to be fixed in place appliances. As such, they would be included in step 5.
Great video, can you make a video on multi dwelling apartments?
Do you have to use the figures in the book for hp conversion? The conversion is not exact, and I'm wondering if that would mess up your answer during the exam
in step no8 you should multiply it by 125%, not 25% ?
We already included 100% of the load in previous steps (either step 4 for A.C. equipment or step 5 for appliance loads) so in step 8 we only need to include an additional 25% to reach a total of 125% for the entire calculation. Hope that helps!
@@electrical1019what is the actual code reference for this because 220.50 isn’t clear about taking 25% of largest motor.
do you have a video for load calculations for multi family and commercial properties
I'm sorry, but wouldn't a 150 Amp Service, be sufficient, since 2014, where the code states your service only needs to support 83% of the load? Your stated load of 156 Amps @ 83% = 129 Amps. Correct?
HI Joey, the rule you are referring to is in regard to the conductor size, not the actual load size. Meaning when you are sizing conductors for a service they only need to be 83% of the ampacity of the service. That is why we can use 4/0 AL wires on a 200A service even though 4/0 AL is not rated for 200 amps. Hope that helps!
Great video. Does your step worksheet have a copyright on it to take in the test with me?
THANKS good explanation, on step 8 you should have added 1680 (25%) + 6720 = 8400 VA from AC motor. ?
Excellent video well explained and broken down step by step. Do you have videos of commercial or multi dwelling calculations.
Yes we do! They can be found on our channel!
Excellent video. Sir plz add videos with more design calculations examples.
We hope to add some soon!
So you chose not to use 75% demand factor on fastened-in-place appliances loads? Neither to use 70% neutral load demand factor for dryer and range?
nec 2023 art 220.53 says you have to have 4 or more to apply 75%. 3 or less is at 100%
Thanks for the video! In reguards to the A/C how do you know to use the alternating current single phase table? as every 240V Air conditioner in the field uses direct current (nuetral is never used, just the two powers.) How do we know to choose alternating current table over the direct current table?
The 2 lines is not direct current. U grossly misunderstand what dc is. DC stands for direct current which comes from a source like a battery and solar. 120 volts is simply half of 240. Neutral is part of the same system of the 240 but is tapped in the center of the secondary transformer of your power. Neutral simply carries the imbalance in your house. 240 is already a balanced system but it is still very much so AC in a single phase system.
Thank you for helping with the great explanation!
Your compressor is a 240v AC motor. Including your blower motor at 120v ac.
Coach one question please. Why 3 VA????
Appreciate this video! Is this 2023 NEC compliant?
At time 13:20… Im confused on how you got 1.15 for 15%
I thought it was done this way 8(.15)=1.2
It’s 115%. 1.15.
Table 220 to 5050 number one you’re adding 5% for each additional 1000 kW over 12,000 kW therefore it’s 115%
Easy to follow, Well done
Thank you Brandon!
On the 2014 NEC I don't see that 310.12 table
Yes, table 310.12 was added in 2020. To find the conductor size needed using a 2014 code, you can simply multiply your service size by 83% and then use the resulting ampacity to select a conductor from table 310.16.
Where can I download the dwelling calculation paper
On our video "Graphics for the national electrical code" we provide a link to download them as well as provided step by step instruction on putting them in your code book!
@@electrical1019 oh, thank you
The air conditioning was omitted, so wouldn't the biggest motor be the garbage disposal that needs to be multiplied by 25%?
I agree with this statement, please advise coach
I thought the electric heat would be the 25%. With 9600VA vs he AC with 6720VA ?.
Thank you for your videos they help tremendously.
I have a question. When calculating the amps from horsepower the formula is :
(Hp x 746)/(volts x phase x eff x pf)
Why not use that formula if the info is given?
Thx and God bless
How would I find the eff?
VA is not "Volts times Amps" that's Watts. It is Volt-Amperes in the same sense that Foot-Pounds are not simply feet times pounds but a "moment arm" of so many pounds across at the end of a foot long lever.
You are absolutely correct; however, in terms of practical application when doing a load calculation and when sizing branch/feeder circuits in the field, they are treated the same. Since this material is also intended to be a theory or electrical terminology instructional video, we don't try to explain this during the lesson. We do hope to be able to upload some material on theory including the difference between real power and apparent power, etc. in the future though!
Does step 1 represent Lighting & Receps?
yes, except laundry and small apps
Do these formulas apply to multi family too?
No
Very helpful, thank you so much!
Thank you!
From where the table 430.248 get the values? Is not 1hp=746watts? Why if using the table, multiply 28*240 instead of 28*230 to get the power of 5hp? It looks like that motor is 55.5% efficient, so 44.5% of the power input is lost. Seems like the worst situation is used for calculating the loads.
very clear explanation
What about the 83% value
This video was very helpful!!!
You're a legend! Thank you
Thank you, this really helped.
Excellent video!!!!!!
Thank you!
Thanks this helps a lot
Thank you very much
very very good... thank you
Thank you!
Why wouldn’t the electric heat be the largest motor at 9600VA vs the AC at 6720
In step 8?
Saludos,
Los vatios son iguales a los VA, solo cuando las cargas son resistivas.
O sea Factor de potencia = zero.
Cuando hay hay cargas inductivas y/o capacitivas, el angulo entre la coriente y el voltaje no es zero(0).
Watts= VA COS zeta
Zeta es el angulo entre la Watts y VA.
This calculation assumes all inductive loads are power factor 1
Found you guys randomly online. I'm in Franklin lol
My question pertains to selection of conductors. I selected my conductors from Table 310.16 under the 75 degree column, since it wasn't specified what the terminal ratings were. I selected 2/0 copper rated at 175 amps rather than 1/0 rated at 150 amps. When should you use Table 310.16 over Table 310.12? Thank you for this video btw. You helped clear up a couple of my other questions. It's tough to not be confused with General/Optional Methods involving single and multi-family dwellings.
Hi Mac, Table 310.12 can only be used according to the requirements of 310.12(A) through (D), which basically say for any dwelling using a single phase service you are allowed to use table 310.12 to size your conductors based on the service size. The only point of table 310.12 is that is already does the math of 310.12(A), which states you can size your conductors based on 83% of the service size. In other words, if we were sizing conductors for a 200A service, we would only need conductors rated at 83% of 200A, which would be 166A. As we can see in table 310.12, for a 200A service a #2/0 copper wire is called out, which is rated at 175A using the 75 degrees column. Hope that helps!
Why is the EVSE load (7200 watts) or nameplate not added to this calculation?
Thank you for information
Phenomenal educator. Thank YOU!
In step #8 you didn't increase the motor by 25% according to the instructions, you just took 25% of the motor. In other words, instead of using 125% of the AC motor, you only used 25%. Why?
Correct me if I'm wrong... in addition to the "keep load" ...he added in the additional 1680 to the total
He added that to the total. So it actually is an increase. I thought the same thing at the time but then I saw what he did with it and it still works. The whole point is to get the total watts to find the minimum amp needed. As long as those watts are all added to the total then it works.
Looks like a really good job for an excel spreadsheet.
1.25% x ACmotor is the process
Thank you 😊
how 1800+3000=8856 ??
I thought you had to increase the ac (largest motor) by 125% per 220.60.
Since we removed that motor from the calculation in step 4, it is no longer considered when determining the largest motor. Hope that helps!
I'm still confused.. if we removed the motor because of step 4 heating and ac.. why are we using the motor.. also where did 25% in lue of 125% come from? Thanks
@@williamdepatie2654 I’m also confused on this could you clarify ?
Please clarify, I thought the largest motor would be the electric heat at 9600 VA for the 25%
Great
I was taught that if you omit the AC motor you don’t use that for 125% of your largest motor. So the way I was taught was I would use 125% of the largest motor I used in my calculations which would be the garbage disposal.
Quote from @electrical1019:
Prior to the 2020 NEC you would be correct, but in the 2020 and 2023 there was an update that now requires the A.C. to be used even if it was originally omitted from the calculation. If you are in a jurisdiction that uses the 2017 NEC or older, than you are correct; you would use the next largest motor if the A.C. was the largest.
Holy shit! As someone who went to college for electrical engineering, this is the most convoluted shit I have ever seen. Great way to make simple math seem complicated. WOW! I TRULY AM AT A LOSS. 😅
Thanks for the video =)
Thank you sir
Thank you very much. Good bless you. Amazing tutorial.
Can we calculate same way for sub panel?
Hi there, the NEC doesn't really have a stance on what load has to be considered for a sub panel, other than if continuous loads, motor loads, etc. will be fed from the panel in which case the 125% rule would apply to the breaker supplying the panel. I recommend sizing sub panels based on the actual load needing to be served (i.e., if you are feeding a combined total of 20,000 watts on a sub panel then I would size that to breaker able to carry that much load). Hope that helps!